H a n d s o n, p r o j e c t b a s e d

Working with Multiple Files
Let’s add more books to analyze. But before we do, let’s move the bulk of 
this program to a function called 
count_words()
. By doing so, it will be easier 
to run the analysis for multiple books:
 word_count.py 
def count_words(filename):
u
"""Count the approximate number of words in a file."""
try:
with open(filename, encoding='utf-8') as f:
contents = f.read() 
except FileNotFoundError:
print(f"Sorry, the file {filename} does not exist.")
else:
words = contents.split()
num_words = len(words)
print(f"The file {filename} has about {num_words} words.")
filename = 'alice.txt'
count_words(filename)
Most of this code is unchanged. We simply indented it and moved it 
into the body of 
count_words()
. It’s a good habit to keep comments up to date 
when you’re modifying a program, so we changed the comment to a doc-
string and reworded it slightly u.

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200
Chapter 10
Now we can write a simple loop to count the words in any text we want 
to analyze. We do this by storing the names of the files we want to analyze 
in a list, and then we call 
count_words()
for each file in the list. We’ll try to 
count the words for Alice in Wonderland, Siddhartha, Moby Dick, and Little 
Women, which are all available in the public domain. I’ve intentionally left 
siddhartha.txt out of the directory containing word_count.py, so we can see 
how well our program handles a missing file:
def count_words(filename):
--snip--
filenames = ['alice.txt', 'siddhartha.txt', 'moby_dick.txt', 'little_women.txt']
for filename in filenames:
count_words(filename)
The missing siddhartha.txt file has no effect on the rest of the program’s 
execution:
The file alice.txt has about 29465 words. 
Sorry, the file siddhartha.txt does not exist. 
The file moby_dick.txt has about 215830 words.
The file little_women.txt has about 189079 words. 
Using the 
try
-
except
block in this example provides two significant 
advantages. We prevent our users from seeing a traceback, and we let the 
program continue analyzing the texts it’s able to find. If we don’t catch 
the 
FileNotFoundError
that siddhartha.txt raised, the user would see a full 
traceback, and the program would stop running after trying to analyze 
Siddhartha. It would never analyze Moby Dick or Little Women.